BMW has filed a patent application for an adaptive cooling system for its motorcycles. As explained in the documentation, the cooling device is generally designed based on the highest expected power demand, which may occur in the case of extreme operating conditions. In everyday situations with lower performance requirements for the cooling system, this is accordingly “oversized”.
If you take a closer look at the vast kidney-shaped grille on modern BMW cars, you quickly notice that it is a decorative decoy rather than a real air intake. That's actually because, in the pursuit of better aerodynamics, BMW uses louvers that close the main grilles on several models when maximum cooling is not required - and now the same idea is being developed for motorcycles .
A BMW patent application revealed what the company dryly calls a "tilting device having a cooling device with a movable air guiding device." The illustrations clearly show a shutter-type system arranged in front of the radiator of a liquid-cooled boxer twin. Much like cars that use a similar system, the idea is to allow enough cooling to satisfy a high-performance engine running at full load, but also to provide improved aerodynamics when the engine is not being stressed and pumping out as much heat.
The patent explains the problem by saying that in pursuit of cooling efficiency, motorcycle radiators are mounted where they are exposed to as much airflow as possible, inevitably creating a substantial aerodynamic obstacle. The problem is compounded by the fact that the cooling system must be designed to cope with extreme weather or performance conditions, unlike those that will be encountered on a daily basis. According to the terms of BMW's patent application: “The cooling device is generally designed based on the greatest expected power demand, which may occur in the case of extreme operating conditions. In everyday situations with lower performance requirements for the cooling system, it is correspondingly “oversized”.
Although the excess cooling capacity of a conventional motorcycle's radiator is addressed by the use of a thermostat to regulate the flow of coolant into the radiator, this does not reduce aerodynamic drag and resulting inefficiency caused by the presence of the radiator itself. This is where the idea of active shutters comes in. Much like the system already used on BMW cars, the company's patent suggests using a Venetian blind-style air guide system in front of the radiator, operated in unison by a single servo to open or close the intake depending on cooling needs.
Depending on the angle and position of the radiator and these flaps – and you can be sure that the final version will be much more subtle than BMW's simplistic patent illustrations, seen here – the aerodynamic benefits promise to be substantial. When the louvers are closed, fully or partially, air is redirected around the radiator rather than through it, reducing drag and improving efficiency.
While we can't draw too many conclusions from the patent drawings, the decision to illustrate the idea on a GS-style motorcycle could be significant, as a new boxer R 1300 GS is under development and is expected to be unveiled this year for the 2024 model range. Given that BMW already mass-produces an active grille system on millions of cars, translating it to motorcycles should not prove an extremely onerous task if the benefits prove as important as the patent application suggests.
